Airport approach lighting



June 4, 1957 i D. 1. coeems ETAL 2,794,967

AIRPORT APPROACH LIGHTING Filed March 31, 1948 a Sheets-Sheet 1 Donald LCo in; Harold Hgins INVENTORS ATTORNEY June 4, 1957 D. l. CQGGINS ETAL 2,794,967

'AIRPORT APPROACH LIGHTING s Shets-Shet s s .m J .m m d a 2 2 m m 7 7 i a x n mm U M. Q 2 E T 2 2 Q v5 w 2 a N i mcmw mm. m l a A 3 v Filed larch 51, 1948 BY G ATTORNEY June 4, 1957 D. 1. coeems ETAL 2,794,967

I AIRPORT APPRoAcH LIGHTING Filed March '31, 1948 a Sheets-Sheet 2 Bunch) lloggins Harohi. lleins INVENTORS Bag '3 AJTOR NEY United States Patent C AIRPORT APPROACH LIGHTING Donald I. Coggins, M'elrose, and Harold Heins, Dorchester, Mass.,;assignors to Sylvania Electric Products Inc., Salem, Mass.,-a corporation of Massachusetts ApplicationMarch 31, 1948,'Serial'N0.18,2 54

12 Claims. (Cl.-34i -26) lia'vefound that a series of lighted tubes, for example longneon tubes set along the approach with the tubes perpendicular to it in a'horizontal plane forms a ladder of light helpful to'thepilot. The'neon lighting by itself forms a sort'of artificial horizon,-but in" extremely heavy fog, smoke or thelike; this is not suflicient, and we find 'a" series" of sequentially flashing beacons set'along the app'roztchftb belu's'efu'l. The beacons may flash one after the" other, the beacon nearest the end of the runway flashing" last, an'd'thesequence then beginning over again. "this-provides-anintensny bright sort of lightning flash, directed toward the landing point, and very impressive 'fromthe air'. Because of the shortduration of the flash in a'iparticula'r lamp, a very great amount of energy can be usedinstantaneously in each lamp without overheating. In practice we have used lamps giving, for example, 8:000j000or mor'e'pe'al candle-power.

The sequentiaYflash" tends to attract the pilots attention,,to reduce the glare'andblanketing effects of fog, to giife'a'directiveefi'ect towardthe runway, and to be easily distinguished from other lights by its color, which is preferablya bluish white as produced by a high-intensity discharge in xenon.

Otherfe'atures, objects and advantages of the invention willbe apparent from the following. specificationtaken inc n'ne'ctionwiththe accompanying drawings, in which: .F are 1" is a schematic view of the installation of beacons 'aloiig'lthea'pproach and runway;

Figure 2 isa front view of one ofthe beacons;

, Figure" 3 is a side View of the neon sign part of the beacon;

Figure4'is a'sideview of the flashingpart of the beacon; and

Figure Sis-a schematic view of the arrangement and cir'cuitsto controlthesystem. I V

Iii Figure l the approach lights 1 are set along the approach to runwa 'z; As shown in Figure 2 each of the approach lights 1' may comprise 4 parallel neon tubes 3, each 6 feet long" set' in front of, and extending outward from thesides .of'a lamp 4 of the flashing beacon type-4. The flashing. beacon lamp 4 is'preferablyset at the focus of a reflector 6 having a shape'of paraboloid of revolution or other suitable shape. The neon tubes 3 may be arranged-in frontof, and extending on'each side of-the flash beacon, each neon bar being set as in Figure 3, at the approximate-focus of a' parabolic or other suitable trough reflec't'Or' S The-whole'unit' may be arranged in a'hOuSiI'ig -ZS, with the'flash reflector 6" in the middle and the troiigh reflectors" 5on each side. The'fl'ash tube 4 is-set in-its reflector directly behind and centered with "ice respect to the neon'bars 3, whose re'flectorsS, doubt,

of course, extend across the'middleof the housing 28. The neon tubes Smay'be operated in the usual man'ne'r from transformers 7 for example as shown in Figure 5, the transformers being connected to the usual'alt'ernating current line through a switch 8; For convenience'only a few of the neon lamps are shown in thi diagram. The flashing beacons 4 may be operated from any circuit which will operate them in sequential flashes with the proper amount of power. A typical circuit is shown schematically in Figure 5where the lamp 4 hasits main electrodes 9 and 10 connected directly across a condenser 22' of high capacity, for example, 30 microfarads which in turn is connected across a direct current line for example of 1800 volts in' series with an appropriate resistor 11' tolimit the chargingcurrent and to prevent discharge of the condenser from shorting the direct current line. The lamp may preferably be such that connection across the condenser will not of itself produce a discharge, the discharge occurring only when the proper starting voltage is connected to thesta'rtin'g or trigger electrode 12. This electrode 12 isconnected to one end of a D. C. line and to one end of the secondary 13 of a transformer having the'primary l4 also connected to one end of the D. Cline.

Theduration'of' the flash is less than 500 microseconds and preferably ZOO microsec'ondsor less, 50 microseconds or even just'a few microseconds being sometimes used. The short" flash appears to greatly reduce the glare and fog blanketing or light scattering usually present with steady o'r'long' flash sources.

one endlS oflthe primary 14'ofthe transformer is connectedto one'end ofth'e D. C. line; the other end-16 of the primary being connected to one terminal 17 of a condenser whose other terminal 18 is connected tothe sa'rn'e' side 19 of the 0. line as is theend 15 of the transformer primary 14. The terminal 17 of the condenser 1-718' is connected to the other side 200i the D.' C. line through-a voltage divider 21. The connection between the end 16' of theprimary 14-- and the terminal 17 of the condenser is completedwith the normally-open contacts 23,24of a switch. A-cam 25 operates to close contacts 23, 24' when it turns so that the projection 2 6 pushes up contact 24. The closing of these contacts allows condenser 1718' to'discharge into the primary of transformer 14, causing a higher voltage to appear across the secondary to act on trigger electrode 12 to start the flash in the lamp. The duration of the flash is quitesho'rt, being determined by the capacity of the condenser 22 andthetotal'resistance and inductance in the circuit throughwhich it discharges, that is by the time constant of the circuit, this time constant being kept very smallto insure a short flash. The time length of flash is not affected by the time the contacts 23, 24 are together, as long as they are together long enough for the condenser 17-'18 to discharge, and as long as they open soon enough to allow the condenser to charge sufficiently.

The resistances 1 1 and 21 should be large enough to prevent the discharge from reacting seriously on the D. C. supply line, yet small enough to insure-that the condensers will charge sufliciently in the short interval between flashes. The circuits for the flash lamps, of which for-convenience only three are shown, operate similarly. The cams 25, may be all mounted on the same shaft 34, turned by motor 33, with their projections 26 being'set' at different angles with some reference point on the shaft to insure that each lamp flashes at its proper time, in the sequence. The sequence switches for flashing may, if desired, be any of the usual timing switches used for neon sign control, modified if necessary to give the proper timing. The timing may be providedby radio, carrier current or other form of control if desired. Switch 27 controls the D. C, circuit.

In one embodiment of the invention, we use 48 lighting units 1, spaced apart appropriate distances along a length of 2800 feet in front of a runway set up .for instrument landing. All of the units have the parallel neon tubes set perpendicular to. the approach and parallel to the horizontal. Only half of the units have the addition of the flashing beacon. In some cases, the units may be placed closer together at the beginning of the approach than at the end. The runway itself may be .illumined by its own separate lighting system 30, approach lighting system ending where the runway begins.

In some. cases, a unit may be set at the beginning of the runway, with the neon red of the bars or discharge tubes replaced by green bars, such as fluorescent tubing, to show where the runway begins, and similar green lighting units may be placed along the runway. The flashing beacon may be used with some of these green units, as in the case of the red. Mercury-argon discharge tubes for example, with an internal coating of manganeseactivated zinc orthosilicate on the tubes, may provide the green light, although in some cases the mercury may not be desired. The lights may be provided in different colors of bars or flash tubes for runway lights, reference lights, obstruction lights and the like.

The beams from each of the lighting units in the approach system should be set at such angles with the horizontal as to provide optimum pilot visibility when following a normal glide for severe weather conditions. In some cases, the beam may also be toed-in or set at a slight angle toward the line of approach to the runway.

The system can be made quite flexible, by inserting switches allowing the use of any one to four neon bars" of light, and allowing the use of either neon or flash beacon, or. both. But best results in severe weather will be obtained by the combination of both, so that the sequential, directed flash of tremendous candlepower will guide the pilot when he is too far away to see the neon lighting, and then as he draws nearer, the neon artificial horizon will further guide him until he is on the runway. We have found that a flashing light of itself is difficult to orient, for its exact position is. hard for the pilot to determine. The flashing lights may appear to jump around and make it diflicult for the pilot to visualize a straight line. For this reason, a faint background of contrasting red neon light is very helpful, enabling the pilot to orient himself better with the flashing lights when the neon comes into view. The flashing light of itself is visible to the pilot at greater distance, and does not appear to the eye to have the hazy background of its own scattered light which a powerful steady beam would have. r

The contrast of the neon red background lights and the blue-white flash, like a trolley-wire flash, is very eflective. The use of multiple bars of neontubing for the background lighting is generally more effective than a single bar, for it gives a larger area of light of definite shape and better visibility. If desired, as indicated in Figure 5, the flashing beacon may be installed not in every lighting unit in the series, but only in alternateunits, if desired. With the system described, a period of one-half second was used for the period from the flashing of the beacon furthest from the runway to the flashing of the beacon nearest the runway. This corresponds to flashing the series of lamps at a speed of about 3600 miles per hour. Since there were 24 flashing units, successive beacons flashed about second apart. The sequence was such that when the beacon nearest the runway flashed, the same second elapsed before the beacon furthest from the runway flashed, and then the successive beacons along the approach flashed A second apart. This timing was found very effective, but can be varied; in some cases a sequence other than that progressing uniformly along the approach may be desired.

The flashing beacon 4 may have a base 31 set into a socket 32 projecting from reflector 6, and may comprise a length of glass tubing, sealed with anelectrode 9, 10

at each end and having a filling of xenon gas at a pressure The glass tubing i of about 40 millimeters, for example. may be coiled into a helix and may have a protective cover 29, set into the base 31. If desired, the beacon lamp may be of the type described in application Serial No. 320, filed January 2, 1948, by E. T. Casellini et al., now Patent No. 2,492,619, preferably in a larger size than the specific embodiment shown in that application. Gases other than xenon may be used, but the latter is preferable for its bluish white light.

By use of a very small source at the exactfocus of a sharply-beamed reflector, a considerable increase in the candlepower and distance of penetration of the beam can be obtained. A pilot otf-course may completely miss such a narrow beam, however, so we prefer a fairly wide beam angle so that the flashing beacon can be seen as much as 40 to 60 degrees from the axis of its beam. This can be found more readily by a pilot otfcourse, and makes his job less like looking for a needle in a haystack, for a pilot is very likely to be off course in a heavy fog. The wide beam helps the pilot when he needs it most.

The foregoing specific embodiment of the invention is given by way of explanation and not of limitation. Various modifications can be made in the invention as long as its principles are maintained. For example, the invention may be used along the approach to a dock for a ship instead of along the approach to a runway for an airplane, and the flashing beacons maybe in fixtures separate from those containing the neon bars, so long as they are aligned properly to guide the landing.

In addition to the visual advantages noted the sequential flashing of the tubes has the further advantage of preventing the current surge which would occur if a number of the lamps were flashed at the same time over the same line. When the sequence of flashing proceeds towards the runway it is more easily visible to the pilot than when it proceeds in the opposite direction because if the pilot is proceeding at high speed in one direction and the sequential flash in the other direction the time available for the pilot to see the flash is reduced.

An application Serial No. 645,625,based on the present application, was filed on March 12, 1957.

What we claim is:

1. An airport approach lighting system comprising: a series of lighting units spaced along the approach, each unit comprising a set of several long straight parallel neon lighting tubes each. tube being parallel to the horizontal and perpendicular to the approach, and a highintensity flash-type beacon lamp set in a reflector behind said neon tubes; means for supplying energy for lighting all the neon tubes of the lighting units in said series at the same time; and means for supplying energy for lighting the beacon lamps of said series and for controlling their discharge sequentially one after the other in short flashes at intervals such that the resultant flashes along the series of beacons simulate a lightning flash pointed toward the runway.

2. An airport approach lighting system comprising a series of high-intensity blue-white Xenon beacons spaced apart substantially along the approach, means for flashing said beacons in predetermined sequence at intervals such that the resultant flashes along the series of beacons simulate a lightning flash pointed toward the runway, a series of neon red discharge tubes spaced along the approach severally assembled with said Xenon beacons, and means for operating said discharge tubes steadily While said other means is flashing said xenon beacons.

3. An airport approach lighting system comprising a series of beacons spaced apart substantially along the approach leading to the end of a runway, means for flashing said beacons in succession at intervals such that the resultant flashes along the series of beacons simulates a lightning flash pointed toward the runway, and a second series of beacons, each beacon in said second series being at substantially the same position as a beacon of said first series, and means for operating said second series of beacons continuously while said first series is flashing.

4. The combination of claim 3, in which the flashing beacons and the continuously-operating beacons are of diflerent colors.

5. The combination of claim 3, in which the flashing beacons emit white light and the continuously operating beacons emit red.

6. The combination of claim 3, in which the beam from each beacon in the flashing series has a beam wide enough to be visible 60 from its axis.

7. An airport approach lighting system comprising a series of beacons spaced apart substantially along the approach leading to the end of the runway, means for flashing said beacons in succession at intervals such that the resultant series of flashes along the series of beacons simulate a lightning flash pointed toward the runway, and a second series of beacons spaced apart substantially along the same approach, the beacons in said second series comprising long straight light bars parallel to the horizontal and perpendicular to the approach, and means for operating said second series of beacons continuously while said first series is flashing.

8. The combination of claim 7, in which the flashing beacons and the continuously-operating beacons are of difierent colors.

9. The combination of claim 7, in which the flashing beacons emit white light and the continuously operating beacons emit red.

10. The combination of claim 7, in which the beam from each beacon in the flashing series has a beam wide enough to be visible 60 from its axis.

11. The combination of claim 7, in which each beacon in the flashing series has a wide beam angle so that the flashing beacon can be seen as much as to degrees from the axis of the beam.

12. The combination of claim 3, in which each flashing beacon has a wide beam angle so that the flashing beacons can be seen as much as 40 to 60 degrees from the aXis of the beam.

References Cited in the file of this patent UNITED STATES PATENTS 2,155,295 Bartow Apr. 18, 1939 2,350,594 Dallas June 6, 1944 2,402,109 Williams June 11, 1946 2,449,063 Edgerton Sept. 14, 1948 2,457,968 Allen et a1. Jan. 4, 1949 2,582,742 Barton Jan. 15, 1952 2,602,850 Cline July 8, 1952 

